The present invention relates to an electric motor having a control drive means and particularly to a technique effectively applied to an electric power steering apparatus for vehicles. And, the present invention, in particular, relates to a technique effectively applied to an electric power steering apparatus used in a rack-and-pinion type steering apparatus.
To assist steering torque of a vehicle, so-called power steering apparatuses are used in many vehicles in recent years, and various power steering apparatuses, such as a hydraulic type, an electric type, and the like have been proposed. Of these power steering apparatuses, a known electric power steering apparatus applied to a rack-and-pinion type of steering apparatus will be one called a rack assist type which obtains a steering assist force by an electric motor provided coaxially on the rack shaft. This type uses an electric motor, which incorporates a field magnetic device, an armature, and the like in a cylindrical yoke, and the steering torque is assisted by this electric motor.
FIG. 19 is a view which explains an example of the rack assist type of power steering apparatus using this kind of electric motor. In the electric type of power steering apparatus shown in FIG. 19, an electric motor 52 is provided to be coaxial relative to the rack shaft 51 and steering assist force generated by the electric motor 52 is transmitted to the rack shaft 51 through a ball screw mechanism 53. Further, the steering wheel is rotated by the steering assist force together with a manual handling force, thereby reducing steering burdens of a driver.
The rack shaft 51 is connected with steering wheels by tie rods, knuckle arms, and the like provided at both ends thereof. The rack shaft 51 is connected by a rack-and-pinion manner to a steering shaft 54 connected to a steering handle or the like and reciprocates in left and right direction in FIG. 19 by steering of the driver. The electric motor 52 is constructed such that a cylindrical armature shaft 56 and a field magnetic device 57 are coaxially inserted in a cylindrical yoke 55, and an electric power is supplied from a power supply section 58. The field magnetic device 57 comprises a magnetic 59 attached on the inner circumferential portion of the yoke 55 and an armature core 60 attached on the outer circumferential portion of the armature shaft 56. The turning force generated by the electric motor 52 is transmitted as reciprocal motion in the axial direction to the rack shaft 51 through a ball screw mechanism 53 provided at the left end of the armature shaft 56 in FIG. 19, and thus, the steering force is assisted.
The power supply section 58 is provided with a brush 61 and a commutator 62 which makes slidable contact with the brush, and the electric power is supplied to the armature portion of the electric motor 52 through these components. The brush 61 is contained and held in a brush holder 63 and is pressed against the commutator with a predetermined pressure by a spring member not shown. A terminal plate 65 is welded to an end of a pigtail 64 of the brush 61. The terminal plate 65 penetrates the housing 66 and projects to the outside. A coupler 67 is attached to the projected terminal plate 65. Thus, the terminal for power supply is formed.
Meanwhile, there has been a proposed apparatus for incorporating control elements such as FETs and the like in the power supply section and for forming integrally a power steering apparatus and a control device section thereof. For example, in Japanese Patent Application Laid Open No. 6-255504, a power steering apparatus is described. In this apparatus, a hollow chamber is formed at the connecting portion where a housing containing a brushless motor and a housing holding a handle shaft are connected with each other, and a power circuit unit which contains FETs and circuit boards in the hollow chamber is provided. Further, Japanese Patent Application Laid-Open No. 8-26125 describes a power steering apparatus in which FETs and boards are contained in a gear box housing where a steering shaft is held and connected with a motor yoke.
In the electronic motor used in the apparatus shown in FIG. 19 or the above example, the power supply section thereof is provided at the connecting portion where an opening edge side of the yoke, the housing (or yoke) of the electric motor side, and the housing of the steering shaft side are connected to each other. It is therefore possible to incorporate relatively easily a brush, a control circuit, and the like in the vicinity of the opening edge of the yoke or a dividing surface. Even in this kind of power steering apparatus using an electric motor, the control circuit or the like can be incorporated so as to be inserted in the vicinity of the dividing surface. Therefore, integration of the apparatus body with the control drive section can be achieved with ease, and there is no problem caused in assembling operation.
However, in an electric motor which uses a cylindrical yoke provided with a side wall at one end thereof and is provided with a power supply section in the side wall side, the power supply section is not situated at the opening portion. Therefore, the control drive section cannot be simply integrated like the above example. That is, if a control drive section is integrally incorporated into this kind of electric motor, various components must be assembled deep into the yoke from the opening side thereof. This results in a drawback in assembling operation.
Also, there is such a type of a power steering apparatus that the housing and yoke in the steering shaft side are formed integrally, a power supply section, an armature, a field magnetic device, and the like are assembled therein, and these components are coupled with another housing containing a ball screw mechanism. The power supply section cannot be situated near a driving portion therebetween. Therefore, the control drive section cannot be integrated easily like the above example. In this type of power steering apparatus, an end side of the yoke of the housing in the steering shaft side is formed in a cylindrical shape which is closed except a rack shaft insertion portion, and the power supply section is provided at a deepest portion of a closed end. Consequently, also in this kind of power steering apparatus, if the control drive section is integrally incorporated, various components must be assembled deep in the housing. So, there are difficulties in assembling operation. Therefore, it is not possible to easily adopt a structure that a space for a control section is formed at a part of the housing like the foregoing example and control elements and boards are assembled in the space. Improvement has hence been demanded in this respect.
The present invention therefore has an object of integrally providing a control drive section with the apparatus body in this kind of electric motor without reducing efficiency of the assembling operation. Also, another object of the present invention is to integrally provide a control drive section of an electric power steering apparatus with the apparatus body without reducing efficiency of the assembling operation.
The above and other related objects and novelty features of the invention will be apparent from reading of the following specification and the accompanying drawings.
An electric motor according to the present invention comprises a cylindrical housing having a side wall at one end portion thereof and is characterized in that a control drive means for controlling and driving the electric motor is provided at an end portion in a side of the side wall inside the housing or on an outer surface of the side wall. As a result of this, even in an electric motor having an electric motor which is provided deep in the housing, the control drive means can be integrally provided with the electric motor without hindering the assembling operation.
In this case, the control drive means may be contained at the end portion in the side of the side wall inside the housing, the side wall may have an opening portion for communicating with inside and outside of the housing, and the control drive means may be electrically connected with the outside of the housing through the opening portion. Further, the control drive means may be provided inside the housing so as to directly contact to the side wall, and thereby heat generated from the control drive means can thereby be efficiently radiated through the housing. The contact between the control drive means and the side wall conceptually includes a modification that not only the surface of the casing in the control drive means but also exposed control drive elements, circuit elements and the like are kept in contact with the side wall. Note that presence or absence of a brush is not asked.
Also, in case where an electric power is supplied with an electric motor by a brush, a brush holder for containing the brush and control drive means for controlling and driving the electric motor may be integrally formed. At this time, a unit which integrates the brush holder and the control drive means can be applied to the electric motor having a cylindrical housing with a side wall at one end portion as described above. Note that in this electric motor, the slidable direction of the brush may be the axial direction or radial direction.
Further, in case where the electric motor has a cylindrical yoke with a side wall at one end portion thereof and an electric power is supplied with the electric motor by a brush, a brush holder for containing the brush and the control drive means for controlling and driving the electric motor may be integrated, thereby forming a drive control unit, and the drive control unit may be provided on an outer surface of a side wall of the yoke. As a result of this, even in an electric motor having an electric power supply section which is provided deep in the housing, the control drive means can be integrally provided with the electric motor without hindering the assembling operation.
At this time, an opening portion may be formed in the side wall so as to communicate with inside and outside of the yoke, and the brush may be inserted into the yoke through the opening portion. Also, the drive control unit may be provided outside the yoke so as to directly contact to the side wall. As a result of this, heat generated from the control drive unit can be efficiently radiated through the yoke. Note that the contact between the control drive means and the side wall conceptually includes a modification form that not only the surface of the casing in the control drive means but also exposed control drive means such as FETs, ECUs and the like are kept in contact with the side wall.
Meanwhile, an electric power steering apparatus according to the present invention comprises: a rack shaft connected to steering wheels; a first housing for containing movably the rack shaft and for holding a connecting portion where rack teeth formed on the rack shaft are engaged with a pinion of a steering shaft connected to a steering handle; an electric motor located coaxially around the rack shaft in the first housing, and supplying steering assist force with the rack shaft; a ball screw mechanism for connecting a nut portion connected with a rotor shaft of the electric motor and a screw portion formed on the rack shaft, with each other with a ball member inserted therebetween, and for transmitting rotatory power of the electric motor as steering assist force to the rack shaft; and a second housing containing the ball screw mechanism and connected with the first housing, the power supply section of the electric motor being provided at the first housing in an opposite side of the second housing relative to an axial direction, and is characterized in that a control drive means for controlling and driving the electric motor is provided at a position adjacent to the power supply section of the first housing.
As a result of this, even in a type of electric power steering apparatus with which an electric power supply section is provided deep in the first housing, the control drive means can be provided integrally in first housing without hindering the assembling operation. In this case, the control drive means may be contained at a position adjacent to the power supply section in the first housing.
In addition, an opening portion through which inside and outside of the first housing communicate with each other may be formed so as to face a located position of the control means, and the control drive means and the outside of the first housing may be electrically connected to each other through the opening portion. Also, the control drive means may be contained inside the first housing so as to directly contact to a side wall of the first housing.
Further, in the electric power steering apparatus according to the present invention, a brush holder for containing a brush of the electric motor and a control drive means for controlling and driving the electric motor may be integrated, thereby forming a drive control unit, and the drive control unit may be provided at such a portion as to face the power supply section outside the first housing.
As a result of this, even in a type of electric power steering apparatus with which an electric power supply section is provided deep in the first housing, the control drive means can be integrally provided with first housing without hindering the assembling operation. At this time, an opening portion through which inside and outside of the first housing communicate with each other may be formed, and the brush may be inserted into the first housing through the opening portion. Also, the drive control unit may be provided outside the yoke with the drive control unit (or control drive means such as FETs and ECUs and the like contained therein) kept in direct contact with the first housing.
At this time, an opening portion through which inside and outside of the first housing communicate with each other may be formed, and a brush may be inserted through the opening portion. Also, the control unit may be provided outside the first housing with the control drive unit kept in direct contact with the first housing.
In addition, another electric power steering apparatus according to the present invention comprises: a rack shaft connected to steering wheels; a first housing for containing movably the rack shaft and for holding a connecting portion where rack teeth formed on the rack shaft are engaged with a pinion of a steering shaft connected to a steering handle; an electric motor located coaxially around the rack shaft in the first housing, and supplying a steering assist force with the rack shaft; a ball screw mechanism for connecting a nut portion connected with a rotor shaft of the electric motor and a screw portion formed on the rack shaft, with each other with a ball member inserted therebetween, and transmitting rotatory power of the electric motor as steering assist force to the rack shaft; and a second housing containing the ball screw mechanism, and is characterized in that the first housing has a power supply opening which is formed at such a portion as to face a power supply section of the electric motor and to communicate with inside and outside of the first housing through the power supply opening portion, and a control drive means for controlling and driving the electric motor is integrally provided with the first housing outside the first housing, and is electrically connected to the power supply section through the power supply opening portion.
As a result of this, even in a type of electric power steering apparatus with which an electric power supply section is provided deep in the first housing, the control drive means can be integrally provided with the first housing without hindering the assembling operation. Also, since the control drive means is provided outside the housing apart from the power supply section, the control drive means does not receive harmful influences from dust caused by abrasion of the brush.
In this case, a second opening portion, through which a slidable contact portion between a commutator of the electric motor and a brush can be observed may be formed at such a portion as to face the power supply section of the electric motor. As a result of this, a state of slidable contact between a brash of the power supply portion and a commutator can be easily observed.
Also, the control drive means may be provided with a terminal plate which is inserted in the first housing through a power supply opening portion and can be observed through a second opening portion, and the terminal plate may be welded through the second opening portion to a contact plate electrically connected to a brush of the electric motor.
Further, the control drive means may be constructed from providing an element for controlling and driving the electric motor on a heat radiation plate made of metal, and the control drive means may be attached onto the first housing with the heat radiation plate kept in direct contact with the first housing. As a result of this, it is possible to improve the heat radiation characteristic of the control drive mean.